Surgical instrument for performing epidural anesthesia

ABSTRACT

Surgical instrument for epidural anesthesia comprising a needle and catheter associated therewith which slides in the needle. The catheter has a set of main axial reference marks coinciding with an index on the needle. A reading will indicate the length of the catheter extending from the distal end of the needle. The catheter also includes a set of auxiliary reference marks distinguishable from the main reference marks.

The present invention relates to the field of surgical instrumentscomprising a needle and an associated catheter capable of sliding insidethe needle, in particular for performing epidural anesthesia.

Epidural anesthesia is a technique that is widespread at present, and asshown in FIG. 1 it consists in putting a catheter C into place in theepidural space P of a patient in order to inject an anesthetic by meansof a needle A which is provided at its distal end 5 with a taperingchamfer tip, also known as a Tuohy needle.

To perform epidural anesthesia, the anesthetist generally begins byinserting the needle A in the back of the patient until the distal end 5of the needle penetrates into the epidural space P, then the catheter Cis inserted via the proximal opening 10 of the needle until itpenetrates into the epidural space P via the distal end 5 of the needle.

In order to avoid trauma to this sensitive region of the patient, it isimportant to avoid pushing the needle in too deep, and thus to know thelength of needle that has been inserted into the back of the patient. Todo this, a Tuohy needle A of the prior art is generally provided, asshown in FIG. 2, with marks 15 that are spaced apart axially uniformlyalong its length, thereby enabling the anesthetist to deduce bycalculating the length of needle that has been inserted into the back ofthe patient, i.e. by knowing the total number of marks on the needle andby subtracting therefrom the number of marks that remain visible afterthe needle has been inserted.

It is also important to know the length of catheter that has beeninserted into the epidural space, and the catheter C is generallyprovided for this purpose with identical marks uniformly spaced axiallyalong its length. To discover the length of catheter extending in theepidural space P, the anesthetist generally counts the number of markson the catheter C that go in through the proximal opening 10 of theneedle as the catheter is being pushed into the needle and after it hasleft the chamfer thereof, which the anesthetist can feel easily since itbecomes more difficult to urge the catheter into the needle once the endof the catheter has gone beyond the distal end of the needle.Thereafter, the Tuohy needle A is withdrawn while the catheter is leftin place in the epidural space in order to inject an anesthetic solutiontherein.

The anesthetist encounters several difficulties that occur during thevarious steps of performing epidural anesthesia as described above.

Firstly, to know the lengths of needle and of catheter inserted into theback of the patient, the surgeon must note or remember the total numbersof graduations carried by the needle and by the catheter, and mustsubtract therefrom the numbers of graduations that remain visible afterinsertion of the needle or of the catheter, and this is not easily donein the context of a surgical operation.

Also, when the needle is being extracted, the catheter tends to beentrained with the needle because of friction, and it then becomesdifficult to establish with accuracy the length of catheter that remainsin the epidural space after the needle has been withdrawn, which problemis illustrated diagrammatically in FIG. 3.

Finally, since the catheter may remain in place for several hours, thereis a danger of it moving during this period and it is important to knowits position accurately before any further injection of anesthetic.

The present invention provides a surgical instrument comprising a needleand an associated catheter suitable for sliding inside a needle, inparticular for performing epidural anesthesia, remedying the maindifficulties described above.

This surgical instrument is characterized in that the catheter isprovided with a set of main axial marks suitable, when the catheter isinserted in the needle, for coinciding with an index mark defined on theneedle, to indicate merely by reading and without performing anycalculation, the length of catheter extending beyond the distal end ofthe needle, and is provided with a set of auxiliary marks easilydistinguished from the main marks and suitable for indicating, merely bybeing read and without performing any calculations, the length of thecatheter that extends from its distal end to each of said auxiliarymarks.

The present invention also provides a needle and a catheter takenseparately and suitable for use in forming a surgical instrument of theinvention.

Other characteristics and advantages of the invention appear on readingthe following detailed description of a non-limiting embodiment of thepresent invention and on examining the accompanying drawings, in which:

FIG. 1, described above, shows the insertion of a catheter into theepidural space of a patient;

FIG. 2 shows a needle provided with marks that are uniformly spacedapart axially, as described above and illustrating the state of the art;

FIG. 3, described above, illustrates the problems posed in the prior artby withdrawing the needle from the back of the patient while leaving thecatheter in place in the epidural space;

FIG. 4 is a front view of a needle of the invention;

FIG. 5 is a side view in the plane of the front view of FIG. 4, showinga needle of the invention together with its associated catheter,likewise of the invention;

FIG. 6 is a bottom view of the catheter shown in FIG. 5;

FIGS. 7 to 11 show various steps in the performance of epiduralanesthesia using a surgical instrument of the invention; and

FIG. 12 shows how the length of catheter opening out into the epiduralspace is calculated after the needle has been withdrawn.

FIGS. 1 to 3 are described above to illustrate the state of the art.

FIG. 4 shows a needle of the invention given overall reference 100, andcomprising a hollow needle body 110 suitable for being inserted via itsdistal end 1100 into the back of a patient, and provided at its oppositeend 1200 with a coupling endpiece 120. As shown, the distal end 1100 ispreferably tapered in order to form a chamfer 115.

In accordance with an advantageous characteristic of the invention, theneedle 100 is provided on its body 110 with graduations 130 that areaxially distributed therealong, and suitable for showing directly,merely by being read and without performing any calculations, the lengthof the needle extending from the distal end 1100 to each of saidgraduations 130.

Preferably, and as shown, these graduations 130 comprise Arabic numeralsprinted or engraved at one centimeter intervals from the distal end1100, together with spots 135, each placed halfway between saidgraduations 130.

In accordance with another advantageous characteristic of the invention,a cursor 140 is provided that is slidably mounted on the body 110 of theneedle, and that is suitable for bearing against an incision made in thebody of the patient and through which the needle is inserted, so as tomove along the body 110 of the needle through a distance correspondingto the length of needle that has been inserted into the said incision,in a manner that is described in greater detail below.

FIG. 5 shows a surgical instrument of the present invention comprising aneedle 100 as described above with reference to FIG. 4 and an associatedcatheter given reference 200, which catheter is suitable for slidinginside the body 110 and the endpiece 120, and is suitable for beinginserted via an opening 125 provided in the coupling endpiece 120.

In accordance with a characteristic of the invention, the catheter 200is provided with a set of main axial marks referenced 210 suitable, whenthe catheter 200 is inserted in the needle 100, for coinciding with anindex mark I that is defined on the needle to indicate, merely byreading and without performing any calculations, the length of catheterthat extends from the distal end 110 of the needle.

The index mark I can be positioned at various locations along the needle100 without going beyond the ambit of the present invention. The planeof the opening 120 in the coupling endpiece preferably serves as theindex mark I, however, it would naturally be possible to provide awindow in the body 110 of the needle 100, optionally fitted with amagnifying glass or other device suitable for making it easier to readthe marks on the catheter.

Preferably, in accordance with an advantageous characteristic of theinvention, this set of main axial marks 210 comprises regularlyspaced-apart main graduations extending from an origin 211 situated at adistance D from the distal end 2100 of the catheter, where the distanceD corresponds to the distance between the distal end 1100 of the needle100 and the index I defined thereon. As shown in FIG. 5, these maingraduations are spaced apart at one centimeter intervals and theypreferably comprise Arabic numerals placed by etching or printing onceevery centimeter from the origin 211, and separated by lines or spotslocated halfway between them.

The catheter 200 is provided with a set of auxiliary axial marks 220that are easily distinguished from the main marks 210 and that aresuitable for indicating, merely by being read and without performing anycalculations, the length of the catheter extending from its distal end2100 to each of said auxiliary marks 220, as shown in FIG. 6.Preferably, this set of auxiliary marks 220 comprises regularlyspaced-apart auxiliary graduations extending from an origin thatcoincides with the distal end 2100 of the catheter. Also preferably,these auxiliary graduations 220 are Arabic numerals spaced apart at onecentimeter intervals and separated by lines or points placed halfwaybetween two numerals. The main marks and the auxiliary marks areadvantageously disposed on the catheter to form two scales in thevicinity of each other so as to facilitate reading thereof. In avariant, the main marks and the auxiliary marks may be disposed ondiametrically opposite faces of the catheter 200. The main marks 210 andthe auxiliary marks 220 are advantageously of different colors.

The various steps of using a surgical instrument of the presentinvention are described with reference to FIGS. 7 to 11.

The space between the spinous processes is initially anesthetized usingtechniques that are known per se, then the needle 100 fitted with itssliding cursor 140 prepositioned at the distal end 1100 is inserted intothe back D of the patient, the needle 100 also being connected in sealedmanner via the endpiece 120 to a syringe S to constitute what is knownto the person skilled in the art as a gas or a liquid mandrel, dependingon whether the syringe S is filled with a gas or with a liquid. This gasor liquid mandrel technique enables the anesthetist to tell accuratelywhen the distal end 1100 of the needle penetrates into the epiduralspace P. Usually, the anesthetist uses one hand to push the needle 100towards the epidural space P, while using the other hand to keep the gasor liquid mandrel compressed until it collapses, where collapse takesplace when the needle 100 penetrates into the epidural space P, as shownin FIGS. 7 and 8. It will also be seen from these figures that thecursor 140 is placed on the needle 100 at a distance L₀ corresponding tothe length of needle inserted into the body of the patient.

Thereafter, as shown in FIG. 9, the syringe S is disconnected, and thecatheter 200 is inserted in the needle via the opening 125 of theendpiece 120 which also serves as the index mark I.

The catheter is pushed along the needle until it reaches the distal end1100.

The anesthetist can then at any moment, and without performing anycalculations, observe the length L of catheter that has been insertedinto the epidural space P by reading the value 1 of the main graduation210 of the catheter that coincides substantially within the index 125,as illustrated in FIG. 10.

In the example FIG. 10, it can be seen that L=2.5 cm since the index Ilies between the graduations 2 and 3.

After the needle 100 has been withdrawn and merely by reading theauxiliary marks 220 on the catheter 200, the surgeon can discoverwithout performing any calculations the length L₁ of the catheter thatextends inside the body of the patient, and can easily deduce therefromthe length L' of the catheter 200 extending inside the epidural space Pby subtracting the length L₀ given by the value l₀ of the graduation 130of the needle 100 indicated by the cursor 140 from the length L₁ givenby the value l₁ of the auxiliary graduation 220 closest of the body ofthe patient, as shown in FIGS. 11 and 12. In the example of FIGS. 10,11, and 12, the needle has been withdrawn without entraining thecatheter out from the epidural space since L=2.5 cm and L'=L₁ -L₀=6-3.5=2.5 cm=L.

Finally, a surgical instrument of the invention is particularly simpleand rapid in use and may be applied, without going beyond the ambit ofthe invention, to surgical operations other than epidural anesthesia,e.g. other local or regional anesthesias.

I claim:
 1. A surgical instrument for performing epidural anesthesiacomprising:a needle having an index mark defined thereon; and anassociated catheter sliding inside said needle, said catheter having aset of main axial marks that when said catheter is inserted in saidneedle, coincide with said index mark on said needle, to indicate merelyby reading and without performing any calculations, the length of saidcatheter extending beyond the distal end of said needle, said catheterfurther having a set of auxiliary marks easily distinguished from saidmain marks that are suitabe for indicating, merely by being read andwithout performing any calculations, the length of said catheter thatextends from its distal end to each of said auxiliary marks; and acursor that is slidably mounted on said needle, said cursor bearingagainst the edge of an incision through which said needle is insertedand moving along said needle through a distance corresponding to thelength that said needle is inserted into said incision.
 2. A surgicalinstrument according to claim 1, wherein said set of main axial markscomprises regularly spaced-apart main graduations extending from anorigin situated at a distance from the distal end of said catheter, saiddistance corresponding to the distance between the distal end of saidneedle and said index mark defined thereon.
 3. A surgical instrumentaccording to claim 2, wherein said main graduations are spaced apart atone centimeter intervals.
 4. A surgical instrument according to claim 1,wherein said set of auxiliary marks comprises regularly spaced-apartauxiliary graduations extending from an origin that coincides with thedistal end of said catheter.
 5. A surgical instrument according to claim4, wherein said auxiliary graduations are spaced apart at one centimeterintervals.
 6. A surgical instrument according to claim 1, wherein saidmain axial marks and said auxiliary marks are disposed on the catheterto form two scales in the vicinity of each other that facilitates thereading thereof.
 7. A surgical instrument for performing epiduralanesthesia comprising:a needle having an index mark defined thereon; andan associated catheter sliding inside said needle, said catheter havinga set of main axial marks that when said catheter is inserted in saidneedle, coincide with said index mark on said needle, to indicate merelyby reading and without performing any calculations, the length of saidcatheter extending beyond the distal end of said needle, said catheterfurther having a set of auxiliary marks easily distinguished from saidmain marks that are suitable for indicating, merely by being read andwithout performing any calculations, the length of said catheter thatextends from its distal end to each of said auxiliary marks, whereinsaid main axial marks and said auxiliary marks are of different colors.8. A process of performing epidural anesthesia utilizing a needle thathas axially spaced-apart graduations suitable for indicating directly,merely by reading and without performing any calculations, the length ofsaid needle extending from its distal end to each of said graduations;that is adapted to receive a catheter suitable for sliding inside saidneedle, said catheter being provided with axial marks comprisingregularly spaced-apart graduations extending from an origin thatcoincides with the distal end of said catheter and suitable forindicating, merely by being read and without performing anycalculations, the length of the catheter that extends from its distalend to each of said marks; and that is provided with a cursor that isslidably mounted on said needle so as to bear against the edge of anincision through which said needle is to be inserted, comprising thefollowing steps:a) inserting into a patient said needle until saidneedle penetrates into the epidural space, said cursor moving along saidneedle through a distance corresponding to the length of said needleinserted into said incision, said cursor being prepositioned at thedistal end of said needle; b) inserting said catheter into said needleand pushing said catheter into the epidural space; c) withdrawing saidneedle; and d) subtracting the length given by the value of thegraduation of the needle indicated by said cursor from the length givenby the value of the graduation of the catheter closest of the body ofthe patient, in order to determine the length of the catheter extendinginside the epidural space so as to insure that said catheter iscorrectly positioned within said epidural space before anesthetic isinjected using said catheter.